1. Field of the Invention
The present invention relates to a soft start bridge rectifier circuit which limits in-rush current and provides short-circuit/overload protection.
2. Description of the Related Art
Conventional bridge rectifier circuits are not well equipped to handle high start-up currents and short-circuits which stress circuit components such as fuses, bridge diodes and smoothing capacitors. Typically, for example, the occurrence of an output short circuit destroys a protection fuse between the power supply and the bridge rectifier, requiring replacement of the fuse. To limit the in-rush current at turn-on, conventional circuits include a thermistor or a relay in series with the output of the rectifier bridge. However, thermistor protection, although inexpensive, is suitable only for low-power applications. Relay protection, while more reliable and efficient than a thermistor, presents a significant cost premium, typically 50% to more than 100% of the bridge rectifier cost, and occupies a significant amount of space, usually more than the bridge rectifier itself.
Therefore, a need exists for a self-contained bridge rectifier circuit which can be provided in a module or package similar to that of a conventional bridge rectifier, but which also provides in-rush current protection on start-up and short-circuit protection during operation without a significant cost premium.